Data are presented for the reaction ep → ep π 0 at a nominal four-momentum transfer squared of 0.5 (GeV/ c ) 2 . The data were obtained using an extracted electron beam from NINA and two magnetic spectrometers for coincidence detection of the electron and proton. Details are given of the experimental method and the results are given for isobar masses in the range 1.19 – 1.73 GeV/ c 2 .
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The inclusive A(e,e') cross section for $x \simeq 1$ was measured on $~2$H, C, Fe, and Au for momentum transfers $Q~2$ from 1-7 (GeV/c)$~2$. The scaling behavior of the data was examined in the region of transition from y-scaling to x-scaling. Throughout this transitional region, the data exhibit $\xi$-scaling, reminiscent of the Bloom-Gilman duality seen in free nucleon scattering.
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The differential cross section for the reaction H2(γ,p)n has been measured at several center-of-mass angles ranging from 50° to 143° for photon energies between 0.8 and 1.8 GeV. The experiment was performed at the SLAC-NPAS facility with the use of the 1.6 GeV/c spectrometer to detect the high energy protons produced by a bremsstrahlung beam directed at a liquid deuterium target. Contributions from concurrent disintegration by the residual electron beam were determined by measuring the proton yield without the Cu photon radiator. At angles not very far from 90°, the energy dependence of the cross sections is consistent with predictions of scaling using counting rules for constituent quarks. At least one theoretical calculation based on a meson-baryon picture of the reaction is able to reproduce the magnitude and energy dependence of the 90° cross section. The angular distribution exhibits a large enhancement at backward angles at the higher energies.
THE QUOTED ERRORS ARE STATISTICAL ONLY.
A systematic set of measurements of the global transverse energy distributions, dσ/dET and dET/dη, from beams of protons, O16 and Si28 at 14.6A GeV/c, incident on targets ranging from Be to Au is presented. The detector was a semicircular array of lead-glass blocks, covering polar angles 9°<θ<32°, whose total response provides a good measure of the produced particle yield in the central rapidity region of these reactions. Proton-nucleus spectra exhibit a similar shape on the high-energy tail, independent of target, suggesting that produced particles in such events arise mostly from the first collision of the projectile proton. For targets heavier than Cu, the high-energy edges of the oxygen-nucleus spectra, and of the silicon-nucleus spectra, reach ratios consistent with the geometry of central collisions. Angular distributions, dET/dη, are characterized by Gaussian fits, and an acceptance-independent form of the differential cross section is found, based on the maximum value of dET/dη. The projectile dependence of nucleus-nucleus spectra is studied in terms of two very different models: simple energy scaling and the wounded projectile nucleon model of p+A convolutions.
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Multiplicities in semi-inclusive deep-inelastic scattering are presented for each charge state of \pi^\pm and K^\pm mesons. The data were collected by the HERMES experiment at the HERA storage ring using 27.6 GeV electron and positron beams incident on a hydrogen or deuterium gas target. The results are presented as a function of the kinematic quantities x_B, Q^2, z, and P_h\perp. They represent a unique data set for identified hadrons that will significantly enhance our understanding of the fragmentation of quarks into final-state hadrons in deep-inelastic scattering.
pi+ multiplicities from HERMES, Target: H, Target: D, VM subtracted.
pi- multiplicities from HERMES, Target: H, Target: D, VM subtracted.
K+ multiplicities from HERMES, Target: H, Target: D, VM subtracted.
Virtual photoproduction of J/ ψ mesons has been measured for 280 GeV muon iron interactions in an iron/scintillator calorimeter target. The J/ψ's were identified by their decay into muon pairs. 315 events were observed, about half of which were elastic. The t , Q 2 and v distributions of these elastic events are presented. The v dependence is measured between 40 and 180 Mev and compared with lower energy photoproduction results. The Q 2 dependence is compared with the predictions of the vector dominance model.
TPRIME DISTRIBUTION OF ELASTIC J/PSI EVENTS FOR ALL Q2 AND NU WITH 280 GEV MUON BEAM.
NORMALIZED Q**2 DISTRIBUTION OF ELASTIC J/PSI EVENTS FOR ALL NU AND T WITH 280 GEV MUON BEAM.
EXTRAPOLATION OF Q**2 AND T DEPENDENCE TO CALCULATE D(SIG)/DT AT Q**2=0 AND T=0 FOR ELASTIC J/PSI PHOTOPRODUCTION PER NUCLEON.
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AVERAGE OVER ALL TARGETS.
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Measurements ofKs0, Λ and\(\bar \Lambda \) production in π− nucleus (C, Cu, Pb) interactions are presented. The experiment was carried out with the streamer chamber spectrometer RISK using a π− beam of ∼40 GeV/c and a trigger requiring a secondary charged particle with transverse momentum above 1.1 GeV/c. Production cross sections, relative production rates and distributions of Feynmanx and transverse momentum squared as well as correlations between theV0 and the trigger particle are presented. The results are compared and found to be in agreement withKs0, Λ and\(\bar \Lambda \) data from untriggered π−p and π−C interactions, except for the relative production rate of antilambdas which is about to times larger in high-pt collisions. Our results can be well interpreted within the dual topological unitarization model.
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Dimuon and trimuon events have been studied in deep inelastic muon scattering on an iron target at an incident muon energy of 200 GeV. The events are shown to originate mainly from charm production. Comparison of the measured cross sections with data taken at higher muon energies shows that charm production originates predominantly from transverse virtual photons. Within the framework of the photon gluon fusion model this indicates that the parity of the gluon is odd.
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Nucleon structure functions obtained from neutrino and anti-neutrino scattering on iron nuclei at high energies (Ev=30 to 250 GeV) are presented. These results are compared with the results of other lepton-nucleon scattering experiments. The structure functions are used to test the validity of the Gross-Llewellyn-smith sum rule, which measures the number of valence quarks in the nucleons, and to obtain leading and second order QCD fits.
Measured charged current total cross section.
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